Net Interest Revenue (Components Of Interest Revenue And Interest Expenses) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net Interest Revenue [Abstract]
Deposits with banks	$ 42	$ 27
U.S. Treasury and federal agencies	199	206
State and political subdivisions	54	56
Other investments	405	355
Securities purchased under resale agreements	9	10
Loans and leases	55	80
Other interest-earning assets	1	0
Total interest revenue	765	734
Deposits	53	58
Short-term borrowings	18	27
Long-term debt	66	71
Other interest-bearing liabilities	3	1
Total interest expense	140	157
Net interest revenue	$ 625	$ 577